The present invention relates to cladding metals upon metallic substrates.
There are many known and long practiced methods for improving the resistance of fabricated or semifabricated metal (including elements, alloys and compounds) to wear, galling, spalling, deformation, corrosion, heating and/or erosion. These include overcoating the surface of the metal and modification of the composition and/or microstructure of the surface through such techniques as carburizing, nitriding, siliconizing, diffusion hardening, hard surfacing (welding a high-alloy layer to the surface), flame hardening, induction hardening and physical modification (e.g. peening). The overcoating methods include electroplating chromium or nickel onto the surface and roll cladding (for sheet form or wire form mill products). Surfaces may also be enhanced by cladding on materials through melting at the substrate surface, such as by laying rods of hard material on the metallic surface and melting by passing the flame of an oxy-acetylene torch thereover. Surfaces may also be enhanced by forming alloys in situ through deposition of minor alloy components and heating with a laser to produce melting and diffusion as taught in the co-pending application of Gnanamuthu, et al., Ser. No. 431,240, filed Jan. 7, 1974.
It is an important object of the present invention to provide a cladding method effective to produce high adherence of a thick layer of metal to the surface of a substrate.
It is a further object of the invention to provide fine and homogeneous microstructure within the clad-on layer consistent with the preceding object.
It is a further object of the invention to provide high and uniform hardness within the clad-on layer consistent with one or more of the preceding objects.
It is a further object of the invention to minimize interdiffusion between cladding and substrate materials consistent with one or more of the preceding objects.
It is a further object of the invention to provide a smooth clad surface consistent with one or more of the preceding objects.
It is a further object of the invention to provide high density - low porosity surface layers of materials consistent with one or more of the preceding objects.
It is a further object of the invention to utilize standard equipments borrowed from other major purposes and not necessarily dedicated to surface modification consistent with one or more of the preceding objects.
It is a further object of the invention to provide flexibility of process control consistent with one or more of the preceding objects.
It is a further object of the invention to minimize incidental effects on the substrate below the surface layer consistent with one or more of the preceding objects.
It is a further object of the invention to provide minimal working time and related substrate preparation and posttreatment times consistent with one or more of the preceding objects.